1. Field of the Invention
The present invention relates to a magnetic recording device having a magnetic head which reads and writes magnetic information while moving relative to a magnetic recording medium, and more particularly, relates to an improved magnetic recording device having a first actuator for coarsely adjusting the movement of a magnetic head relative to a magnetic recording medium, and a second actuator for finely adjusting the movement of the magnetic head.
2. Description of the Related Art
Conventionally, a magnetic recording device with a configuration shown in FIG. 5 is known as an information recording device for use in personal computers.
In a magnetic recording device M shown in FIG. 5, a plurality of disklike magnetic disks 100, which are coated with a magnetic film, are rotatably housed in a box-shaped chassis 101. Magnetic heads 102 are placed on the front or back sides of the magnetic disks 100 so as to move relative to the magnetic disks 100. Each of the magnetic heads 102 is supported by a base 105 via a load beam 103 shaped like an elongated triangular plate and an arm 104. The base 105 is movably supported in the chassis 101. That is, in the configuration shown in FIG. 5, the magnetic head 102 is moved relative to the magnetic disk 100 in the radial direction by movement of the base 105 so as to read out magnetic information recorded on a desired position of the magnetic disk 100 or to write magnetic information on a desired position of the magnetic disk 100.
Regarding the driving structure for the base 105 shown in FIG. 5, the base 105 is rotated on a rotating shaft 106 in parallel with the rotating shaft of the magnetic disk 100, and the magnetic head 102 is thereby moved in the radial direction above (or below) the magnetic disk 100. The base 105 may be driven in various ways, for example, by a driving structure using a voice coil motor or by a driving structure using a linear motor.
In the magnetic disk device M shown in FIG. 5, various signals, such as control signals for the magnetic heads 102, signals of magnetic information read by the magnetic heads 102, signals of magnetic information to be written on the magnetic disks 100 by the magnetic heads 102, and selection signals for the magnetic heads 102, must be exchanged between a main control device and the magnetic heads 102.
For this reason, conventionally, a main control device 107 disposed in the chassis 101 and the base 105 are connected by a flexible printed circuit board 108, and various wires are laid on the printed circuit board 108 so as to connect the main control device 107 and the magnetic heads 102.
FIG. 6 schematically shows the state in which the printed circuit board 108, connectors 109 of the main control device 107, and the magnetic heads 102 are connected.
In this example, two magnetic disks 100 are stacked one above the other, and magnetic heads 102 are placed on the upper and lower sides of the magnetic disks 100. Two connecting wires 111 are connected to each of the magnetic heads 102 and are routed onto the printed circuit board 108. The connecting wires 111 are connected to terminals 115 disposed on one side of a control element 112 placed on the printed circuit board 108. Terminals 116 on the other side of the control element 112 are connected to the connectors 109 of the main control device 107 via a plurality of connecting wires 113.
The connecting wires 111 connected to the four magnetic heads 102 are connected in order from the top to the terminals 115 which are also arranged on one side of the control element 112 in order from the top in FIG. 6, and are laid out so as not to intersect on the printed circuit board 108. The terminals 116 on the other side of the control element 112 are connected to the connector 109 of the main control device 107 via the connecting wires 113 which are laid in parallel so as not to intersect on the printed circuit board 108. In the terminals 115 shown in FIG. 6, Vcc represents a power input terminal, R/W represents a read/write mode switching terminal for the magnetic head 102, RD represents a read signal output terminal, HS0 and HS1 represent magnetic head selection terminals, WDI represents a write data input terminal, WUS represents a writing enable signal terminal, and GND represents a ground terminal.
With recent increases in recording density of magnetic disks, the width of tracks formed on the magnetic disks have been reduced year by year. Conventionally, the width of tracks (thin information writing areas formed on a magnetic disk in the circumferential direction) is set so that approximately forty thousand tracks can be formed per inch, for example, the track width has been reduced to approximately 0.5xc3x9710xe2x88x926 m. Therefore, if the track width is further reduced, it may be difficult for the magnetic head to precisely trace the tracks of such reduced width in the driving mechanism for the magnetic head utilizing rotation of the base 105, the driving mechanism utilizing a voice coil motor, or the linear driving mechanism. For example, it is thought that stability of the control system cannot respond to further reduction in track width in the existing driving mechanism for the magnetic head because of structural limitations of a bearing system.
Accordingly, attempts have been made to precisely and finely adjust the position of the magnetic head by providing a second actuator, which allows finer movement, in addition to the conventional driving mechanism. While various elements have been proposed as the second actuator, a piezoelectric actuator has attracted great attention as a promising driving element.
While the piezoelectric actuator is characterized in being capable of finely adjusting the position of the magnetic head by controlling current application thereto, when wires of the piezoelectric actuator are incorporated in the wiring structure shown in FIG. 6 and the control element 112, the number of wires is increased. This makes it difficult to lay the wires in parallel on the printed circuit board 108 so as not to intersect with one another.
While the voltage for controlling the magnetic head is usually approximately xc2x15 V or xc2x13.3 V, the control voltage for the piezoelectric actuator is approximately xc2x130V, which is high. Therefore, it is difficult to incorporate both a transistor for controlling the piezoelectric actuator and a transistor for controlling the magnetic head in the same control element 112, because this increases the withstand voltage of the transistor for the magnetic head.
When the wires of the piezoelectric actuator are laid on the printed circuit board 108 in addition to the wires of the magnetic head, the number of wires on the printed circuit board 108 is increased, and flexural rigidity of the printed circuit board 108 is also increased. The increase in flexural rigidity of the printed circuit board 108 increases the resistance when the base 105 shown in FIG. 5 rotates. As a result, when the position of the magnetic head 102 is finely adjusted corresponding to the fine tracks, the printed circuit board 108 having increased flexural rigidity hinders improvement of the tracking accuracy. Therefore, it is preferable that the number of wires on the printed circuit board 108 be as small as possible.
Although the problems of intersection of wires can be easily overcome by providing a jumper switch on the printed circuit board 108, this makes assembly and adjustment of the printed circuit board 108 more troublesome and decreases assembly efficiency and reliability.
The present invention has been made in view of the above-described circumstances, and an object of the invention is to provide a structure for a magnetic recording device having a first actuator for coarsely adjusting the position of a magnetic head relative to a magnetic disk and a second actuator for finely adjusting the position of the magnetic head, in which wires for the magnetic head and wires for the second actuator can be laid out in parallel on a flexible wiring board so that they do not intersect with one another.
In the present invention, it is possible to apply current only to a magnetic head and a second actuator necessary to be driven, of a plurality of magnetic heads and a plurality of actuators, and to prevent current from being applied to the other magnetic heads and the other second actuators. This reduces power consumption and prevents heat generation.
Another object of the present invention is to provide a structure for a magnetic recording device having a first actuator and a second actuator, in which flexural rigidity of a flexible wiring board is prevented from being increased by minimizing the number of wires laid thereon in order to limit increases in the load on a driving system for the magnetic head and to improve tracking accuracy.
In order to achieve the above objects, according to an aspect of the present invention, there is provided a magnetic recording device including: a plurality of magnetic heads for moving relative to a magnetic recording medium so as to read information from the magnetic recording medium; first actuators for moving the magnetic heads relative to the magnetic recording medium; second actuators disposed respectively corresponding to the magnetic heads so as to finely adjust the positions of the respective magnetic heads relative to the magnetic recording medium; a flexible wiring board having connecting wires for the first actuators and the second actuators thereon; and a control element disposed on the flexible wiring board and connected to the connecting wires, wherein the control element includes: a plurality of actuator-driving-signal connecting terminals respectively connected to the second actuators; an actuator-driving-signal input terminal to which driving voltage for the second actuators is input from a control device; a plurality of connecting wires for connecting the actuator-driving-signal connecting terminals to the actuator-driving-signal input terminal; signal selection elements respectively incorporated in the connecting wires; and a decoder for selecting one of the signal selection elements so as to connect a specific one of the actuator-driving-signal input terminals to the actuator-driving-signal input terminal.
Even in a case in which the number of wires laid on the flexible wiring board may be increased because of the structure including the first actuators for moving the magnetic heads and the second actuators for finely moving the magnetic heads and having a driving voltage different from that of the first actuators, the wires for the second actuators are switched by switching among the signal selection elements incorporated in the connecting wires for the actuator-driving-signal input terminals by the decoder, which allows a single driving signal input terminal to be commonly used for the second actuators and which reduces the number of wires. This minimizes increases in number of wires to be laid on the flexible wiring board. Therefore, it is possible to easily lay out the wires in parallel on the flexible wiring board and to simplify the wiring structure.
Preferably, the driving voltage for the second actuators is set to be higher than the driving voltage for the magnetic heads.
Preferably, the first actuators are used for coarse adjustment so as to move the magnetic heads in the direction of width of tracks on the magnetic recording medium with information recorded thereon, and the second actuators are used for fine adjustment so as to move the magnetic heads in the direction of width of the tracks. Preferably, the first actuators each include an arm, a load beam mounted at the leading end of the arm, and an elastic flexure mounted at the leading end of the load beam, sliders are disposed at the end of the flexures so as to have the magnetic heads therein, and the second actuators are placed between the arms and the flexures.
In the magnetic recording device having the first actuators for coarse adjustment and the second actuators for fine adjustment, the magnetic heads incorporated in the sliders may be each supported via the arm, the load beam, and the flexure, and the second actuator may be each placed between the arm and the flexure. This facilitates fine adjustment of the position of the magnetic heads.
Preferably, two or more head-driving-signal lines are laid on the flexible wiring board, head-driving-signal connecting terminals respectively connected to the head-driving-signal lines are disposed in the control element, the actuator-driving-signal connecting terminals are disposed adjacent to the head-driving-signal connecting terminals in the control element, and a plurality of terminal sets of the head-driving-signal connecting terminals for the magnetic heads and the actuator-driving-signal connecting terminals for the second actuators corresponding thereto are arranged in line in the control element.
When the head-driving-signal connecting terminals connected to the head-driving-signal lines and the actuator-driving-signal connecting terminals connected to the actuator-driving-signal lines are arranged in line adjacent to each other in the control element so as to form terminal sets, the head-driving-signal lines and the actuator-driving-signal lines can be easily arranged in parallel on the flexible wiring board.
Preferably, the head-driving-signal lines connected to the head-driving-signal connecting terminals and the actuator-driving-signal lines connected to the actuator-driving-signal connecting terminals are arranged in parallel on the flexible wiring board so as not to intersect with one another.
Since these signal lines are thus arranged in parallel on the flexible wiring board so as not to intersect, intersections of the lines are not formed, and noise due to the intersections will not occur. This eliminates the necessity for placing a jumper on the flexible wiring board and improves reliability of wiring on the flexible wiring board.
Preferably, the head-driving-signal connecting terminals and the actuator-driving-signal connecting terminals are repeatedly arranged in the same order on one side of the control element.
Such arrangement allows the wires to be more easily arranged in parallel on the flexible wiring board.
Preferably, the magnetic heads are merged magnetic heads each having a reading element for reading information from the magnetic recording medium and a writing element for writing information, and a plurality of the head-driving-signal lines are disposed for the reading element and a plurality of the head-driving-signal lines are disposed for the writing element.
Since the number of signal lines is increased in the merged magnetic head, it is more difficult to arrange the signal lines in parallel on the flexible wiring board. However, multiple wires can be arranged in parallel so as not to intersect by arranging the terminals in line in the control element, as described above.
Preferably, the magnetic heads are merged magnetic heads each having a reading element for reading information from the magnetic recording medium and a writing element for writing information, a plurality of the head-driving-signal lines are disposed for the reading element and a plurality of the head-driving-signal lines are disposed for the writing element, and the decoder disposed on the control element has a switching means for switching between transmission of read information from the reading element to the control device and transmission of written information from the control device to the writing element.
The switching means incorporated in the decoder switches between transmission of read information from the reading element to the control device and transmission of written information from the control device to the writing element, and selection of the second actuators is made under the control of the signal selection elements and the decoder. Therefore, both the selection of the second actuators and the driving of the reading element and the writing element can be controlled by the decoder. Even when the voltage for the signal systems of the reading element and the writing element and the driving control voltage for the second actuators are substantially different, both the actuators and the elements can be controlled by the single decoder without any trouble.
Preferably, the signal selection elements includes a photocoupler composed of a diode and a switching element.
Even when the voltage for the second actuator driving system is high, xc2x130 V, in contrast to the low voltage of xc2x13.3 V or xc2x15 V for the magnetic head driving system, since both the circuits thereof are electrically separated by the photocoupler, signal selection can be performed so that the circuits do not have any influence on each other.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.